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Monday, March 09, 2009

A Monday meander - Cyclones, drought and water wars

It was raining quite heavily here in Sydney when I got up, so I checked the weather.

To this point, Queensland has been spared serious damage from Cyclone Hamish, a category four storm, as it moves south down the coast. The photo from the ABC shows Mackay on the edge of the storm.

So long as the storm stays out to sea Queensland will be drenched, but not seriously damaged.

The rain in Sydney is not connected with Hamish - Hamish is a long way from here - but comes from another system. Victoria remains generally dry. The low cloud over the south of the state is keeping temperatures down, but has little moisture in it.

In South Australia there are clouds over the west and north of the state, bringing sometimes heavy rain to the usually very dry area that includes Lake Eyre.

This, Australia's largest salt lake, fills rarely. The water that has been coming down the long channels all the way from Queensland has reached the lake. Now flood warnings have been issues because of the rain coming from the south.

The Channel Country, the name given to the area through which the generally dry rivers flow south to Lake Eyre, occupies a special place in Australian history and outback mythology. This is tough harsh country that suddenly blooms as the floods spread across the countryside. There is an explosion of life.

As the European pastoralists came to understand the country's variable climate, they established chains of properties - vast areas in total larger than many European countries - that allowed them to move stock across large areas as the weather changed. The Channel Country was a key link with stock fattened there after the floods.

Australia is a very dry country. Even now some people die of thirst each year, generally visitors to outback areas whose cars break down or who simply get lost.

One major problem is that there is limited natural surface water in many areas, even some of those areas with better rainfall such as the western slopes and plains adjacent to the New England Tablelands. There the Aborigines used to move widely across the countryside in wet periods, concentrating around rivers and natural water sources during the dry. Animals followed a similar pattern.

The big drought that has been gripping South Eastern Australia will break.

The heavy drought area has been contracting to the south and east as rainfall nibbles around the edges. South East Queensland and New England have been out of drought for some time, although some of the big New England storage dams built during the relatively wet post war period are still at low levels.

A final break in the drought may still be some time in the future. If this drought runs as long as the longest recorded drought, I think that this was the drought over the Second World War period, then it may not break until 2012.

While droughts sometimes break in flooding rains, more often it is a staged process.

Dry ground has first to absorb water. Once soil moisture levels build up, run-off increases. Creeks and rivers start to flow and then flood. This process takes time. 95% of the rainfall in the Murray Darling basin is lost through evaporation and transpiration.

For the benefit of climate nuts, each month the Australian Bureau of Meteorology releases three monthly climate projections. The latest projections released end February suggested the likelihood of above average rain in North Queensland, South Australia and South Western NSW. The South Australian and NSW projections imply some further contraction in drought areas.

I have a strong vested interest in all this.

South Australia's concerns about its Murray River Water have created a political need to find more water for the lower Murray. The amount of water that can be obtained from Victoria and Queensland is limited by existing arrangements. The only "free" water is in Northern New South Wales.

Following the purchase of the water rights of Toorale station and its withdrawal from agricultural production, a decision reportedly costing 100 direct and indirect jobs, the Federal Government has advertised for the purchase of more water rights in the Darling's northern catchment.

Irrigators will sell if the price is right. So we are likely to see further contraction of agricultural production with consequent job losses. I hate to think of the regional economic impact if the current drought over the lower basin were to last to 2012.

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